The present invention relates to a fan wheel with a cup shaped hub with a cup wall provided with a plurality of radially extending vanes and a cup bottom connected with a shaft of a drive motor.
Fan wheels of the above mentioned general type are known in the art. In a known fan wheel the cup bottom has substantially the same thickness as the cup wall. When such a fan wheel is fixedly connected with the shaft of the drive motor, the magnetic force fluctuations occurring in the electric motor due to the armature grooves extending through the magnetic field can propagate through the shaft to the hub and radiated through the vanes as sound transmitted air. The flutes tone produced in this way has a frequency of approximately 630 Hz depending on the size of the hub and is disturbing especially when the fan is used for ventilation of the cooling device for the internal combustion engine of a motor vehicle.